Re: looking for good sound
yeah, an amp is a good idea. tell your stereo shop what it will be going on and they should have some stuff that will not draw too much power from your battery array.
also spend some money on good speakers. buy brands that have been around for a while, they tend to have the better warranties.most 6-1/2 inch speakers will give you decent bass and midrange with the tweeter filling in the rest. many shops have a foam baffle that you place over the magnet and basket of the speaker, its a good thing to have as it will protect the back of the speaker from accidental punctures and will help keep the speaker's mechanical stuff dry
when looking at the stereo itself, look for something that allows you to plug in an ipod or other mp3 device, and getting one that is satellite radio capable will keep you happy and allow you to hear the game while fishing, always a bonus